The invention pertains to a testing apparatus. In particular, the invention pertains to an apparatus for testing an engine speed control governor separate from the engine and a connected load.
A governor 10 shown in FIG. 1 is a device for controlling the speed or load of an engine 12 generally by regulating the engine fuel valve relay 13. The engine 12 may be connected to a generator 14 as an engine-generator set 15 for supplying a load 16. The governor 10 operates by sensing the speed of the engine 12, the characteristics of the load 16, or both, and regulating the fuel supplied to the engine 12. The governor 10 includes a load computer (LC) 18 responsive to voltage and current signals from the load 16 and a speed control unit (SCU) 20 responsive to a speed signal from the engine 12. An amplifier 22 responsive to the load signal provides a compensating signal to the speed control unit 20 as illustrated.
The speed control 20 has a plurality of inputs. The speed control unit 20 may be adjusted by speed adjustment potentiometer 24 to a selected operating frequency. Synchronize input 26 is used by a synchronizing apparatus 27 to adjust the engine speed for synchronizing two generators for parallel operation. Generally speaking, the speed control operates over a predesignated range of frequencies which is established by circuitry internal thereof. The speed adjustment potentiometer 24 is used to trim the speed control unit 20 to a particular desired operating frequency. The sync input 26 is employed to change the control point of the speed control unit 20 momentarily in order to adjust the engine and consequently the generator 14 so that the outputs of the generator may be synchronized and matched with other units, the outputs of which may be combined as hereinafter discussed.
Voltage and current signals produced by the generator 14 are coupled to the load computer 18 in the governor 10. These signals are combined to develop a DC voltage proportional to the product of the in phase components of the current and voltage signals. In actual operation, this voltage is proportional to the true electrical load on the generator 14. This signal may be used to slow the engine down as the load increases, a condition known as speed droop.
When an engine-generator set 15 is operated alone, the load computer 18 is normally not utilized. However, if multiple engine-generator sets feed a common load, it is necessary to equalize the load by means of the load computer 18 whereby the load computer signal is fed back to the speed control unit 20 to balance the outputs of each of the generators in use. Speed droop and load sharing action are achieved by using the voltage output of the load computer 18 to modify the control point of the speed control unit 20. Speed droop amplifier 22 connects the output of the load computer 18 to the speed control unit 20. This causes the speed control unit to reduce its output with increasing load.
Troubleshooting and testing of electronic governors is currently done with the governor 10 installed on the engine 12 (on-engine testing) or by testing the governor 10 separate from the engine 12 by means of separate pieces of test equipment (bench testing). When the governor 10 is tested on the engine 12, at least two technicians are required for safety and to accomplish the test procedures. On-engine testing may also require a third person to operate load bank equipment and other functions. Load testing may be inhibited because a load bank is not available. Also, operating the generator 14 under the control of a potentially faulty or defective governor 10 with a live load risks damaging the connected equipment.
Bench testing requires a variety of testing devices which may not always be available. In particular, power resistors, power supplies and oscillators of the proper power rating may not be readily available. Equipment capable of high power testing is also expensive. Also, even when the equipment is available, the tests are limited.
It is therefore desirable to provide a reliable and safe apparatus for bench testing an engine governor which safely simulates speed and load conditions.